The field of the present invention relates generally to camera positioning systems. For the purpose of this application a camera shall refer to any type of device capable of recording or transmitting either still or moving images including but not limited to conventional cinema cameras, conventional still cameras, television cameras, videotape cameras, digital cameras, CCD cameras, or the like.
Traditionally, camera cranes have been employed to assist in the positioning of cameras at defined locations and orientations to capture the desired shot. Conventional camera cranes are generally comprised of a crane arm (or xe2x80x9cjibxe2x80x9d), a support structure to which the crane arm is mounted, and a xe2x80x9cleveling headxe2x80x9d affixed to the distal end of the crane arm. Typically, the crane arm is pivotally coupled to the support structure in a manner that facilitates the rotation of the crane arm about a vertical and a horizontal axis. The rotation of the crane arm about the vertical axis is generally referred to as crane arm xe2x80x9cswing,xe2x80x9d while the rotation of the crane arm about the horizontal axis is generally referred to as crane arm xe2x80x9cboom.xe2x80x9d In addition to the crane arm being capable of swing and boom, conventional crane arms are often constructed to be adjustable in length, so that the crane arm can xe2x80x9ctelescopexe2x80x9d from one length to another. Thus, the distal end of the crane arm (i.e., the end affixed to the leveling head) is capable of translating through a semi-sphere, the diameter of which is controlled by the overall length of the crane arm, which can be adjusted by telescoping the crane arm. Moreover, camera cranes are often mounted on a rolling platform that is generally referred to as a xe2x80x9cdolly.xe2x80x9d
The leveling head is a mechanism that is typically employed to connect the camera crane arm to a camera mounting structure referred to as a xe2x80x9ccamera head.xe2x80x9d Leveling heads are generally comprised of a leveling mechanism that functions to maintain a xe2x80x9cleveling platexe2x80x9d parallel to a defined plane in response to changes in the boom of the crane arm. As used in this application a xe2x80x9cleveling platexe2x80x9d is a defined member of the leveling head that is adapted to being coupled to the camera head. An example of such a leveling head is disclosed in U.S. Pat. No. 4,943,019, which is hereby incorporated by reference.
Conventional camera heads, in addition to providing a support structure to securely mount the camera, are typically adapted to rotate about a vertical axis (i.e., panning) and a horizontal axis (i.e., tilting) relative to the leveling plate. To facilitate the panning and tilting of the camera head, two independently actuated motor mechanisms are usually employed. The first is often referred to as a xe2x80x9ccamera pan motor,xe2x80x9d which as the name suggests facilitates the panning of the camera head (i.e., the rotation of the camera head about the vertical axis). The second is often referred to as a xe2x80x9ccamera tilt motor,xe2x80x9d which also as the name suggests facilitates the tilting of the camera head (i.e., the rotation of the camera head about the horizontal axis).
In operation, the boom (i.e., the rotation of the crane arm about a horizontal axis), swing (i.e., the rotation of the crane arm about a vertical axis), telescope (i.e., the length of the crane arm), and the movement of the rolling platform or dolly are typically controlled manually by one or more operators or xe2x80x9cgrips.xe2x80x9d The adjustments of the leveling head are usually automated to respond to the change in the boom so as to maintain the camera head generally level to the horizontal plane. The xe2x80x9cpanxe2x80x9d and xe2x80x98tilfxe2x80x99 of the camera head together with the focus of the camera, on the other hand, have been traditionally controlled remotely (usually via electrical circuitry) by another operator, referred to as the xe2x80x9ccamera-operator,xe2x80x9d who is responsible for the composition of the shot (i.e., the field of view and focus of the camera).
Thus, the camera-operator, in fashioning the composition of the shot, must compensate the field of view of the camera by panning and tilting the camera head in response to movements of the crane arm, dolly, and the subject matter being filmed. In light of the complex dynamics of such systems, the camera-operator""s task can be extremely difficult, especially when filming complicated shots. Consequently, situations inevitably arise where the field of view of the camera is not accurately or in a timely fashion compensated for the movements of the crane arm and/or dolly. In addition, situations also arise, with or without movement in the camera crane or dolly, where the field of view of the camera is not accurately compensated for the movement of the subject matter. As a result, considerable expense and time is expended in re-shooting.
To assist the camera operator in achieving the desired composition, some camera heads such as those disclosed in U.S. Pat. Nos. 5,644,377 and 5,835,193, which are hereby incorporated by reference, employ an automated back pan compensation mechanism that, when activated, pans the camera head in a reverse direction relative to the swing of the camera crane arm. The amount of pan compensation may be adjusted by the user prior or during filming. These compensation mechanisms, however, simply reverse pan the camera head in response to changes in the swing of the crane arm without reference to the other potential movements of the camera support structure (e.g., boom, telescope, or dolly movement) or changes in the position of the subject matter being filmed. Furthermore, these compensation mechanisms are not readily suited for achieving accurate back pan compensation in response to changes in the swing of the crane arm. This is so because there is non-linear relationship between changes in the angular position of the camera arm and the desired angular back pan of the camera head. Thus, these systems require adjustment/calibration of the back pan gain, especially when large changes in the swing of crane arm occur. Consequently, these compensation mechanisms, while potentially helpful in assisting the camera operator in panning the camera head in certain circumstances, may not provide suitable assistance in situations in which the movement of the camera support structure is more complex or when a change in the position of the subject matter occurs.
The present invention relates in one aspect to a camera positioning system, whereby the positioning system provides for compensation for the movement of the camera support structure. A separate aspect of the present invention relates to a camera positioning system, whereby the positioning system provides for compensation for the movement of a subject matter. Yet another separate aspect of the present invention relates to a camera positioning system, whereby the positioning system provides for compensation for the movement of both the camera support structure and the subject matter. Two or more of these aspects may be combined.
Additional embodiments, features, variations and advantages of the invention are set forth in the description and accompanying drawings that follow, and are fither evident on consideration thereof.